Creating connections for conference event package participants.

- Add "addExistingCall" method to Connection service wrapper to handle
the creation of new calls for connections which already exist in telephony.
- Fixed but in setIsConference message where an isValidCallId check made
outside of the handler would result in a newly added call NOT being
marked as conferenced due to a race condition.  The MSG_SET_IS_CONFERENCED
handler already checks if the call exists before performing its operation.

Bug: 18057361
Change-Id: I2348c8e6985cd831f2cae56b37dfcb33bae014a8
2 files changed